1. Field of the Invention
The present invention relates to transformers for transforming high voltage, alternating current obtained from a conventional electrical power source to low voltage, direct current power, whereby a battery cell is electrically connected with the transformer and conveniently charged. In particular, the present invention relates to transformers having a plug for plugging into a power source outlet, wherein the plug is foldable so that the transformer can be compactly stored when not in use.
2. Description of the Prior Art
U.S. Pat. No. 5,401,178 discloses a conventional foldable transformer. FIG. 4 of the attached drawings shows the transformer having a plug 50, a pair of rotary pins 46, and a pair of internal circuit connection means 48. Each connection means 48 is pivotally connected via a pivot to a corresponding rotary pin 46, such that each rotary pin 46 is pivotally foldable while maintaining constant electric connection with the connection means 48. The plug 50 further includes a rotatable transverse rod 40, an arcuate engaging block 36, and a spring 38. A concave pivot reception 44 is defined in each end of the rod 40, for receiving a corresponding pivot. The rod 40 also has grooves 42 defined therein, and the block 36 also has a protruding engaging ridge 37 for engaging in the grooves 42. A blind hole 39 is defined in an end of the block 36 opposite to the engaging ridge 37, for receiving one end of the spring 38. A substantially box-shaped storage cavity 32 is defined at a junction between a top surface and a front surface of an insulative enclosure 30. The cavity 32 further has an electrical-connection opening 33, and a pin hole 34 for receiving an opposite end of the spring 38.
In assembly, each fixed pin 48 is inserted into a corresponding electrical-connection opening 33. When the rotary pins 46 and rod 40 are rotated to an open position as indicated in FIG. 4, the spring 38 exerts force such that the ridge 37 firmly engages in the corresponding groove 42. The pins 46 are thus securely held in position, allowing the plug 50 to be conveniently inserted into an AC power source outlet.
However, the plug 50 still has the following shortcomings.
1. Its structure has too many components, making it unduly complicated and difficult to manufacture.
2. The spring 38 is not a reliable component. The spring 38 cannot easily be uniformly mass produced, which causes the quality of various plugs 50 to not be uniform. Furthermore, repeated use of the plug 50 may reduce the resiliency of the spring 38 to the point where the spring 38 becomes dysfunctional.
Accordingly, an improved foldable transformer is required.
Accordingly, an object of the present invention is to provide a plug for a foldable transformer that has a reduced number of components, is easily manufactured and assembled, and is reliable.
In a preferred embodiment, the present invention comprises an insulative enclosure and a plug. The plug is rotatably attached to the enclosure, and electrically connects an electronic circuit within the enclosure with an external power supply. The enclosure includes a storage cavity at the top end thereof. A pair of pin holes is defined in the enclosure at a rear of the cavity. A pair of parallel slots is defined in the enclosure between the pin holes. An arcuate engaging block is integrally formed on a bridge of the enclosure between the slots, by plastic injection. The plug includes a transverse rod, and a pair of rotary pins at opposite ends of the rod. Each rotary pin is pivotally and electrically connected via a pivot to a fixed pin. Each fixed pin is fixed within the corresponding pin hole, and is electrically connected to the electronic circuit. In a folded position, the rotary pins are accommodated entirely within the cavity. A groove defined in the rod engagingly accommodates the engaging block. The rotary pins are manually rotated outwardly from the cavity. The engaging block is released from the groove by the rod pressing against the engaging block and thereby elastically deforming the bridge. The rotary pins are rotated out to an unfolded position where they are perpendicular to the enclosure, and in which another groove defined in the rod engagingly accommodates the engaging block. The rotary pins are then ready to be inserted into a power source.
Other objects, advantages and novel features of the present invention will be drawn from the following detailed embodiment of the present invention with attached drawings, in which: